Q31. In mammals, remnants of the embryonic notochord persist as:
a) Tailbone (coccyx)
b) Skin
c) Intervertebral discs
d) Brain tissue
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Correct Answer: c) Intervertebral discs
Explanation: During mammalian development, the notochord mostly disappears as the vertebral column develops around it. Remnants become the soft, gelatinous core (nucleus pulposus) within the intervertebral discs, which serve as shock absorbers between the vertebrae.
Q32. Which of the following groups possesses a notochord at some point in their life cycle?
a) Fishes
b) Amphibians
c) Birds
d) All of the above
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Correct Answer: d) All of the above
Explanation: All vertebrates (fish, amphibians, reptiles, birds, and mammals) are chordates. This classification implies that a notochord is present at some point during their development. While the notochord might be replaced by the vertebral column, it serves as an important developmental precursor.
Q33. The dorsal, hollow nerve cord found in chordates develops into the:
a) Exoskeleton
b) Central nervous system (brain and spinal cord)
c) Digestive tract
d) Post-anal tail
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Correct Answer: b) Central nervous system (brain and spinal cord)
Explanation: The dorsal, hollow nerve cord is a defining feature of chordates. During development, this structure becomes the central nervous system, consisting of the brain and the spinal cord that runs along the dorsal side of the body.
Q34. Which of the following terms describes animals that maintain a constant body temperature?
a) Ectothermic
b) Endothermic
c) Poikilothermic
d) Thermophilic
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Correct Answer: b) Endothermic
Explanation: Endothermic animals, like birds and mammals, generate internal heat to maintain a stable body temperature. This allows them to stay active in diverse environments but requires greater energy input.
Q35. Animals that rely on external heat sources to regulate their body temperature are called:
a) Ectothermic
b) Endothermic
c) Poikilothermic
d) Heterothermic
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Correct Answer: a) Ectothermic
Explanation: Ectothermic animals (e.g., reptiles, fish) depend on the environment to regulate their body temperature. Behavioral adjustments like basking in the sun or seeking shade are crucial for their survival.
Q36. Warm-blooded animals are more accurately classified as:
a) Ectothermic
b) Endothermic
c) Mesothermic
d) Cold-blooded
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Correct Answer: b) Endothermic
Explanation: While commonly used, “warm-blooded” isn’t scientifically accurate. It’s better to use ‘endothermic’ to describe animals capable of regulating their body temperature internally.
Q37. Which characteristic most clearly distinguishes birds (class Aves) from other vertebrates?
a) Presence of a notochord
b) Four-chambered heart
c) Feathers
d) Endothermy
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Correct Answer: c) Feathers
Explanation: While birds share characteristics with other vertebrates (notochord, four- chambered hearts, endothermy), the presence of feathers is a unique, defining feature of birds. Feathers are essential for flight, insulation, and display.
Q38. Animals that develop within an amniotic egg or within the mother’s uterus are known as:
a) Oviparous
b) Viviparous
c) Amniotes
d) Ovoviviparous
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Correct Answer: c) Amniotes
Explanation: Amniotes (reptiles, birds, mammals) are characterized by the evolution of the amniotic egg, a protective structure allowing development on land. This contrasts with anamniotes (fish, amphibians), whose eggs depend on water.
Q39. Which of the following animals exhibits ovoviviparity?
a) Chicken
b) Platypus
c) Human
d) Some sharks
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Correct Answer: d) Some sharks
Explanation: Ovoviviparous animals hold eggs internally where they hatch, giving the appearance of live birth. Some sharks and snakes display this reproductive strategy, providing nutrition to the growing young within the eggs.